Electrical circuit breakers often have a rotary contact system which features two fixed contacts for connection to a respective current path and also a rotatably supported contact element interacting with a least one of the fixed contacts. The movable contact element mostly embodied in the form of a bridge serves to interrupt and close the circuit. An actuation mechanism, for example in the form of a rocker lever, is used for manual switch-on or switch-off. In the event of a short-circuit the contact bridge should open very quickly through electrodynamic forces independently of the actuation mechanism.
During opening of the contact bridge a switching arc occurs between the contacts which, at very high temperatures, leads to a loss of material at the contacts, known as arc erosion. The very hot solid or gaseous erosion products contaminate and/or damage the surfaces within the switch. This can have a significant effect on the opening function of the switch and can lead to malfunctions. Erosion materials accumulate above all on the function elements of the rotary contact system and, on account of the changes in friction conditions produced thereby, prevent the contacts opening properly in the event of a short-circuit.
Various solutions are known from the prior art which are oriented towards avoiding contamination by erosion materials. These mostly involve mechanical sheathing or encapsulation of specific functional parts of the rotary contact system. These types of mechanical solutions are comparatively expensive since they must be implemented within the smallest space without adversely affecting the proper function of the switch.
At least one embodiment of the invention is directed to covering the surfaces of some or all of the functional parts of the switch at least partly with a protective material, with the protective material involving a viscous, temperature-resistant mass. This applies at least for the function of the switch, especially functional parts relevant to the opening function. The mass used prevents the hot erosion materials being deposited or accumulating on the functionally-relevant subsurfaces and thereby contaminating or damaging said surfaces. This ensures that the proper opening of the switch is not impeded even after a repeated occurrence of erosion materials.